The invention disclosed and claimed herein deals with a novel process of preparing hydroxy functional vegetable oils and the vegetable oils so prepared. Vegetable oils have been familiar to man since prehistoric times and for centuries humans have used plant based fats and oils for food and a variety of other uses. Over the years chemists perfected the science related to the production of oils from agriculture products. Today, millions of pounds of such oils are used in a variety of end user applications. Furthermore, given the finite quantity of petroleum based products, the use of vegetable and plant oils as substitute feed stocks for petroleum is growing exponentially.
Vegetable oils are made up principally of triglycerides containing both saturated and unsaturated fatty acid moieties, wherein the predominant moiety is the unsaturated variety (i.e., the variety having double bond carbon-carbon linkages (C═C) along the fatty acid carbon chain). Even though triglycerides are useful in many chemical applications, there are applications in which their performance can be improved if they are altered to have functionalities different than those that are found in the raw vegetable oil.
For example, triglycerides can be converted to hydroxy functional compounds called “polyols”. The addition of “hydroxyl functionality” is typically accomplished by adding hydroxyl groups (—OH) to the carbons. These polyols are then used as reactants to make polymers. The hydroxyl functional groups in polyols can be reacted with isocyanates to make polyurethanes which are a very versatile group of polymers. Polyurethanes can be used in the form of foams, cast resins, coatings, adhesives, and sealants.
In order to use vegetable oils as feed stocks in polyurethane processes, multiple hydroxyl functionality is required. Some vegetable oils, such as castor oils, have a significant degree of hydroxyl functionality built into them. Other vegetable oils must obtain the required hydroxyl functionality through synthetic means. One such means is the hydroxylation of unsaturated vegetable oils via epoxidation or oxidation of the C═C using hydrogen peroxide (H2O2) followed by ring-opening of the resulting epoxides with proton donors. The present invention is an improvement on this general process.
In addition, most known processes for hydroxylating vegetable oils result in a product that has commercially detrimental aesthetic qualities. For example, many known vegetable based polyols have an unpleasant odor that is carried over into polymer products. Other vegetable based polyols have a degree of coloration that unacceptably tints any polymer made from them.
Vegetable oil based polyols should possess a low acid number (a measure of the remaining fatty acid in the polyols) to function well in urethane systems. Polyols with elevated acid numbers tend to produce sub-optimal polyurethanes because the remaining acids can interfere with catalysts utilized in polymerization reactions and/or participate in unwanted side reactions. Utilizing separate neutralization steps (e.g., adding a base such as KOH to the polyol) can alter the characteristics of the polyol such that its use results in sub-optimal polyurethanes.
Finally, hydrogen peroxide can be explosive under certain conditions and care must be taken to ensure the safety of workers in hydroxylation processes that use hydrogen peroxide as the oxidizing agent for opening the C═C bonds in the fatty acid moieties.
Accordingly, there is a need for a simple, economical, safe, and efficient process for the preparation of polyols that are derived by opening the C═C of the fatty acid moieties of vegetable oils to add hydroxyl groups. In addition, there is a need for simple, economical, safe, and efficiently made polyols that possess a relatively low acid number to allow their use in urethane systems without further neutralization steps.
What has been discovered is a simple, safe, and economical preparative process for the provision of hydroxyl functional polyols of low acid number that are suitable for the formation of polyurethanes, wherein the polyols are derived by opening the alkene groups (C═C bonds) of the unsaturated fatty acid moieties of vegetable oils and adding hydroxyl groups. Also discovered is a unique polyol that is well suited for use in polyurethane applications.